I'm the author of the EthernetDHCP library. I'll promise to eventually push out an update that's compatible with 0019+, it's just that I'm currently extremely short on time and that the significant change of the Ethernet and SPI libs between 0018 and 0019 was entirely unexpected for me.

Kiku, let me thank you again for your work to port EthernetDHCP too 0019+, and yes, please feel free to go ahead and post your changes here, so that others can use them.

Other than that, please use 0018 for now (You can still download it at Arduino.cc), since it might still be a week or two until I have some spare time again.